1. Field of the Invention
The present invention relates to control signaling in the uplink and a control channel for carrying control signal data in the uplink of a communication system.
2. Description of Related Art
Expanded efforts are underway to support the evolution of the Universal Mobile Telecommunications System (UMTS) standard, which describes a network infrastructure implementing a next generation Wideband Code Division Multiple Access (W-CDMA) air interface technology. A UMTS typically includes a radio access network, referred to as a UMTS terrestrial radio access network (UTRAN). The UTRAN may interface with a variety of separate core networks (CN). The core networks in turn may communicate with other external networks (ISDN/PSDN, etc.) to pass information to and from a plurality of wireless users, or user equipments (UEs), that are served by radio network controllers (RNCs) and base transceiver stations (BTSs, also referred to as Node Bs), within the UTRAN, for example.
Standardizing bodies such as the 3rd Generation Partnership Project (3GPP and 3GPP2), a body which drafts technical specifications for the UMTS standard and other cellular technologies, have introduced several advanced technologies in an effort to ensure that any associated control information is carried in an efficient manner. Certain advanced or enabling technologies may include fast scheduling, Adaptive Modulation and Coding (AMC) and Hybrid Automatic Repeat Request (HARQ) technologies. These technologies have been introduced in an effort to improve overall system capacity. In general, a scheduler or scheduling function at a Node B (base station) selects a UE (mobile station) for transmission at a given time, and adaptive modulation and coding allows selection of the appropriate transport format (modulation and coding) for the current channel conditions seen by the UE.
AMC technologies enable a selection of a data rate and a transmission format (i.e., modulation level and channel coding rate) that best “suits” the scheduled user's prevailing channel conditions. Delays and measurement errors result in degraded performance from AMC.
HARQ allows combining of the original transmission with the new transmission, rather than to discard the original transmission. This may greatly improve the probability of correct decoding of the packet. The word “hybrid” in HARQ indicates that Forward Error Correction (FEC) techniques have been used in addition to ARQ techniques. Accordingly, HARQ helps to ensure that transmissions resulting in unsuccessful decoding, by themselves, are not wasted.
While much of the standardization to date has focused on the downlink (forward link from Node B/base station to UE/mobile station), similar enhancements are now being considered for the uplink (reverse link). Further evolution of 3G standards include enhanced uplink (EU) features to support high-speed reverse link packet access (uplink from mobile station to base station). Many of the techniques used in the forward link (i.e., fast scheduling, AMC, HARQ, etc.) may also be usable on the reverse link, so as to improve data rates and system capacity, for example.
In voice-based or circuit-based communication systems, control signaling or scheduling is typically not employed. Once the communication link is established between network and user, the user may transmit continuously, essentially at will, at a fixed data rate. Rate change occurs rarely, if ever, during the duration of the call/connection. The rate change is done by using higher layer signaling between the RNC and the UE. The signaling is carried over the existing communication link and the change is extremely slow and infrequent.
However, packet data-based communication systems require coordination between network and user at a much faster pace, as the packet data is typically transmitted in bursts. Thus, data rates and transmit times may typically be subject to some type of scheduling, since rate, duration and time of user transmission in the uplink may be limited or constrained by the network. Conventionally, this ‘fast coordination’ has been done only in the downlink, i.e., a Node B transmitting signaling and/or control information over a physical channel known as a high-speed shared control channel (HS-SCCH) in the downlink to users the Node B is serving. However, in order to support some of the above enhancements, and to facilitate the above-noted coordination with the network, control signaling may need to be evaluated for the uplink, for purposes of scheduling a user for uplink transmission and coordination with the network.